A loss we need to face: The main concourse of Pennsylvania Station in 1962. The treasure’s now been gone for longer than it existed. Photo: AP

The old Pennsylvania Station, architectural achievement for the ages that it was, has been gone for 50 long years now. And it ain’t coming back.

Isn’t it time to move on?

Manhattan Borough President Scott Stringer and others don’t think so. They cling bittersweetly to the notion that someday soon there will be found a pile of cash big enough, if not to rebuild the old station, at least to fashion a replica using the Farley Post Office building on Eighth Avenue as an anchor.

Dream on, Scott.

Stipulated, tearing the old girl down in 1963 was a mistake — though certainly not the calamity asserted by the city’s cast-everything-in-amber crowd.

Penn Station — like its East Side analogue, Grand Central Terminal — couldn’t stand on its own economically after the passing of America’s railroading era. Even now, Grand Central requires massive direct and indirect public subsidies to keep its architecturally inspiring nose above water.

Whether that was sufficient reason to tear either of them down is open to debate. But it should be kept in mind that Penn Station fell, and Grand Central almost followed, not out of spite or on a whim, but because great cities remain great cities only through renewal and reconstruction. At the time, neither could pay its own way — and reasonable alternative uses for the land they stood on beckoned.

In contrast, the present Penn Station is now the busiest railroad station in America. Yes, it squats with Madison Square Garden plopped down on it like some grotesque cupcake, and so the structure is never going to inspire poets. But it does deliver the fiscal freight.

This should count for a lot — but not to Stringer, along with the Municipal Art Society, the Regional Plan Association and others, who think they have a better idea: the Farley Post Office option.

Somehow, Penn Station is to be folded into that remarkable piece of urban architecture — and then everybody will live happily ever after.

It’s a concept cribbed from the late Sen. Daniel Patrick Moynihan — arguably one of America’s last great public intellectuals, but also a man rarely troubled by detail. And, in this case, the fine print is enough to turn strong minds into Play-Doh.

For example, the scheme would force Amtrak passengers walk roughly an extra mile to get to their trains. Plus:

* The project would cost billions, of which scarcely a penny is in sight. And never mind New York’s ability to generate eye-popping cost over-runs.

* Any number of responsible developers have looked seriously at the undertaking, as well as at some associated notions, smiled politely and walked briskly away.

* Whereupon the proposal was delivered to the custody of the Port Authority, which can be counted on to hold it hostage for eventual agreement to an equally grandiose New Jersey project. (Anyone ignorant of how that works need only investigate the appallingly profligate PATH station boondoggle at Ground Zero.)

So bye-bye to the so-called Moynihan Station project.

There is an alternative, however, and that is to build on the status quo. The Madison Square Garden Co. is in the final stages of investing at least $1 billion into what is essentially a gut-rehab of the Garden, one of the most successful, and famous, entertainment venues in the world.

In return, the company is seeking an open-ended extension of its now-50-year-old operating permit — essentially, into perpetuity.

Stringer opposes this, and on Wednesday he essentially called on the City Council to limit the permit to 10 years — long enough, in his mind, for a miracle to occur.

Easy for him. He’s running for city comptroller this year — and, frankly, MSG isn’t one of the most sympathetic companies operating in New York these days.

But is that how adults do business?

On one hand, there is a pipe dream. On the other, there is a company that already employs 8,500 New Yorkers and is investing hundreds of millions in expansion, renewal and growth.

And standing squarely in the middle is a pinched-vision politician and some pals — none of them with any skin in the game and each dedicated to the notion that New York City’s future lies buried 50 years in its past.